Organosilicon primer compositions

ABSTRACT

This invention provides novel silanes and bis-silylhydrocarbons that contain a plurality of silicon-bonded alkoxy groups and at least one substituent that is bonded to silicon through oxygen and contains at least four carbon atoms, two of which form a terminal group of the formula CH 2  ═CH--. A preferred class of these compounds will cohesively bond polyorganosiloxane elastomers and resins to both organic and inorganic substrates.

This is a divisional of co-pending application Ser. No. 844,057 filed onMar. 26, 1986 now U.S. Pat. No. 4,659,851.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to novel organosilicon compounds. Moreparticularly, this invention relates to organosilicon compoundscontaining one or two silicon atoms, at least two silicon-bonded alkoxygroups and at least one group that is bonded to silicon through oxygenand contains ethylenic unsaturatiion at a terminal position.

2. Description of the Prior Art

Certain types of silanes and other organosilicon compounds containingethylenically unsaturated radicals bonded to silicon by means of anoxygen atom have been disclosed in the prior art.

Reaction products of ethylenically unsaturated epoxide compounds withchlorosilanes or bis-trichlorosilhydrocarbon compounds of the generalformula Cl₃ SiQSiCl₃ where Q represents alkylene, alkenylene, arylene oralkarylene are disclosed in U.S. Pat. No. 3,369,006, which issued toBrown on Feb. 13, 1968. All of these reaction products contain asilicon-bonded chlorinated alkenyloxy radical of the general formulaYCHCLCH₂ OSi, where Y represents an ethylenically unsaturated organicradical containing carbon, hydrogen and, optionally, oxygen and halogen.

1-alkenyloxysilanes wherein an ethylenically unsaturated carbon atom isbonded to an oxygen atom that is in turn bonded to silicon are disclosedin U.S. Pat. No. 3,472,888, which isssued to Bazouin et al on Oct. 14,1969, and in British Patent No. 1,058,866, which issued on Feb. 15,1967. Bazouin describes vinyloxysilanes that are reaction products of achlorosilane, represented by the formula R_(n) SiCl.sub.(4-n), with theenol form of an aldehyde or ketone, the enol compound being representedby the general formula R'R"C═CR'"OH. The products of this reactionexhibit the general formula R_(n) SiO(R'")C═CR'R"_(4-n), where Rrepresents a monovalent organic radical, and R', R" and R'" eachrepresent a hydrogen atom or a monovalent organic radical that is freeof reactive substituents. The compounds described in the British patentcan be represented by the same general formula used for Bazouin'scompounds, with the proviso that the radicals represented by R', R" andR'" optionally contain ethylenic unsaturation which is reactive withcarbon monoxide. The compounds of the British patent are prepared byreacting a terminally unsaturated hydrocarbon with (1) a silanecontaining a silicon-bonded hydrogen atom and (2) carbon monoxide.

The preparation of allyloxytrimethoxysilane is described by D. F.Peppard in articles that begin on pages 70 and 73 of volume 68 of theJournal of the American Chemical Society. The articles were published in1946. The silane was prepared by reacting allyl alcohol withtrimethoxychlorosilane in the presence of pyridine.

SUMMARY OF THE INVENTION

An objective of this invention is to provide novel silanes andbis-silylhydrocarbons that contain a plurality of silicon-bonded alkoxygroups and at least one substituent that is bonded to silicon throughoxygen and contains at least four carbon atoms, two of which form aterminal group of the formula CH₂ ═CH--.

A second objective of this invention is to provide novel organosiliconcompounds that will cohesively bond polyoganosiloxane elastomers andresins to inorganic and organic substrates.

DETAILED DESCRIPTION OF THE INVENTION

The novel compounds of this invention include silanes of the generalformulae

    (R.sup.1 O).sub.n (R.sup.2 O).sub.4-n-p R.sup.3.sub.p Si   Formula 1

and

    R.sup.4 [OSi(OR.sup.2).sub.3-p R.sup.3.sub.p ].sub.2       Formula 2

and organosilicon compounds of the general formulae

    (R.sup.1 O).sub.n (R.sup.2 O).sub.3-n SiR.sup.5 Si(OR.sup.1).sub.r (OR.sup.2).sub.3-r                                        Formula 3

and

    R.sup.4 [OSi(OR.sup.2).sub.2 R.sup.5 Si(OR.sup.2).sub.3 ].sub.2 Formula 4

where

R¹ represents a radical selected from the group consisting of

    CH.sub.2 ═CHCH.sub.2 R.sup.6,                          Formula 5

    CH.sub.2 ═CHR.sup.6 OR.sup.7 --,                       Formula 6

    CH.sub.2 ═CHR.sup.6 OC(O)R.sup.8                       Formula 7

    CH.sub.2 ═CHR.sup.9 C(O)OR.sup.7,                      Formula 8

and

    (CH.sub.2 ═CHR.sup.6 O).sub.2 R.sup.10 ;               Formula 9

R² represents an alkyl radical containing from 1 to 4 carbon atoms;

R³ represents a monovalent hydrocarbon or fluorinated hydrocarbonradical; R⁴ represents a radical selected from the group consisting of

    CH.sub.2 ═CHR.sup.10 <,                                Formula 10

    CH.sub.2 ═CHR.sup.6 OR.sup.10 <,                       Formula 11

    CH.sub.2 ═CHR.sup.6 OC(O)R.sup.10 <,                   Formula 12

and

    CH.sub.2 ═CHR.sup.9 C(O)OR.sup.10 <,                   Formula 13

R⁵ represents hydrocarbylene containing at least 2 carbon atoms;

R⁶ represents a hydrocarbylene or substituted hydrocarbylene radicalwhere the substituent is hydroxyl or alkoxy;

R⁷ is selected from the same group as R⁶, or represents anallyloxy-substituted hydrocarbylene radical with the proviso that R⁷contains at least 2 carbon atoms;

R⁸ is selected from the same group as R⁶ ;

R⁹ represents a single bond or a radical selected from the same group asR⁶ ;

R¹⁰ represents a trivalent hydrocarbon radical;

n is 1 or 2;

p is 0 or 1;

r is 0 or 1; and

_(4-n-p) is at least 2.

In preferred embodiments of the present compounds, R² is methyl orethyl, R³ represents an alkyl, haloalkyl or phenyl, R⁵ and R⁷ eachcontain from 2 to 10 carbon atoms, R⁸ contains from 1 to 10 carbonatoms, R⁹ represents a single bond, alkylene containing from 1 to 10carbon atoms, cycloalkylene or phenylene, and R¹⁰ contains from 3 to 10carbon atoms.

Compounds of this invention wherein R² and R³ of the foregoing formulae1-4 are methyl, R⁵ is ethylene, n is 1 or 2, p is 0 or 1 and r is 0constitute a preferred class that is particularly useful as eitherprimers or adhesion promoters for cohesively bonding polyorganosiloxaneelastomers to a variety of substrates. The silicon-bonded hydrocarbonradicals of the polyorganosiloxane are preferably methyl.

The organosilicon compounds of this invention can be defined as silanes,alpha, omega-disilylalkanes, -disilylcycloalkanes and -disilylarenesthat contain at least two silicon-bonded alkoxy groups per molecule andat least one substituent corresponding to R¹ in the foregoing formulae 1and 3 or one substituent corresponding to R⁴ in formulae 2 and 4.

R¹ is bonded to an oxygen atom that is in turn bonded to silicon andcontains at least four carbon atoms, two of which form an ethylenicallyunsaturated terminal group of the formula CH₂ ═CH--. The remainder of R¹is composed of hydrogen and, optionally, oxygen atoms. In one embodimentR¹ contains two unsaturated terminal groups.

The substituent identified as R⁴ in the preceding formulae 2 and 4 isidentical to R¹, except for the fact that it is trivalent and bonded totwo silicon-bonded oxygen atoms.

The four embodiments of the R¹ and R⁴ substituents defined in thepreceding formulae 5 through 12 are described in detail hereinafter. Inthese embodiments R¹ is the residue remaining following removal of ahydroxyl group from one of five classes of organic compounds. R⁴ is theresidue remaining following removal of two hydroxyl groups from the sameclasses of compounds.

The five classes of organic compounds included within the definitions ofthe R¹ and R⁴ substituents are (1) terminally unsaturated alcohols, (2)phenols containing a terminally unsaturated aliphatic hydrocarbonradical as a substituent, (3) ethers derived from the reaction of either(1) or (2) with either a saturated polyhydric alcohol or a polyhydricphenol, (4) esters derived from the reaction of a terminally unsaturatedcarboxylic acid with either a saturated polyhydric alcohol or apolyhydric phenol and (5) esters derived from the reaction of either (1)or (2) with a saturated aliphatic, a saturated cycloaliphatic or anaromatic hydroxycarboxylic acid.

The compounds of this invention can be prepared by reacting one of thesefive classes of organic compounds with an alkoxysilane or abis-silylhydrocarbon containing silicon-bonded alkoxy groups. Thereaction products contain at least two alkoxy groups per silicon atom.

If the aforementioned organic and organosilicon compounds are reacted insubstantially equimolar quantities the resultant compound of thisinvention will be represented by the foregoing formula 1 or 3, dependingupon whether the organosilicon reactant is a silane or abis-trialkoxysilylhydrocarbon. When one mole of an organic compoundcontaining two or more hydroxyl groups is present for every two moles oforganosilicon compound, the reaction product will conform to theforegoing formula 2 or 4.

In one embodiment, referred to hereinafter as A, R¹ is defined as CH₂═CHCH₂ R⁶ --, and R⁴ is defined as CH₂ ═CHR¹⁰ ═. In these formulae R⁶ isa hydrocarbylene radical that is either unsubstituted or contains atleast one hydroxyl and/or alkoxy group and R¹⁰ is a trivalenthydrocarbon radical. R⁶ preferably represents unsubstituted alkylenecontaining from 1 to 10 or more carbon atoms, hydroxyl substitutedalkylene, hydroxyl substituted alkylene, unsubstituted cyclohexylene,unsubstituted phenylene, hydroxyl- or alkoxy substituted phenylene orthe residue remaining following removal of one of the two terminalhydroxyl groups from a hydroxyl terminated polybutadiene molecule of theformula ##STR1## where q represents an integer from 10 to about 100,inclusive, the value of u is greater than 0 and the sum of s, t and uis 1. Preferably q is between 50 and 60 and u is between 0.5 and 1.0.

In embodiment A, R¹ and R⁴ represent the residue remaining followingremoval of one and two hydroxyl groups, respectively, from either (1) aterminally unsaturated alcohol or (2) a phenol containing a terminallyunsaturated hydrocarbon radical as a substituent. As used in thisspecification the term "terminally unsaturated" implies the presence ofa hydrocarbon radical that includes a CH₂ ═CH--grouping at a terminalposition.

Terminally unsaturated monohydric alcohols useful for preparing thepresent compounds contain at least 4 carbon atoms, and include but arenot limited to 3-buten-1-ol, 3-butene-2-ol, 2-methyl-3-butene-2-ol,5-hexen-1-ol, 9-decene-1-ol, 17-octadecen-1-ol and the isomeric allylsubstituted cyclohexanols.

Terminally unsaturated polyhydric alcohols or partial ethers thereof canbe substituted for a monofunctional alcohol. It will be understood thata terminally unsaturated alcohol containing at least two hydroxyl groupsor a phenol containing at least two hydroxyl groups and a terminallyunsaturated hydrocarbon radical as substituents must be used to preparecompounds of this invention corresponding to the foregoing formula 2 or4.

Monohydric, terminally unsaturated phenols include the isomeric allylphenols and cresols. The definition of R¹ for embodiment A encompassesresidues of diphenols, such as hydroquinone, having as a substituent onthe phenyl ring a terminally unsaturated hydrocarbon radical containingat least 3 carbon atoms. One of the hydroxyl groups of the diphenol canbe reacted to form an ether or ester as, for example, in eugenol.

In a second embodiment of the present compounds, referred to hereinafteras embodiment B, R¹ is defined as CH₂ ═CHR⁹ C(O)OR⁷ --and R⁴ is definedas CH₂ ═CHR⁹ C(O)OR¹⁰ <. R⁷ is selected from the same group ofhydrocarbylene radicals as defined hereinabove for R⁶ or R' canrepresent an allyloxy substituted hydrocarbylene radical, with theproviso that R⁷ contains at least two carbon atoms. R⁹ is also selectedfrom the same group of radicals as R⁶ or it can represent a single bondand R¹⁰ represents a trivalent hydrocarbon radical.

For the compounds of embodiment B, R¹ and R⁴ represent the residuesremaining following removal of one and two hydroxyl groups,respectively, from the alcohol portion of an ester derived from thereaction of a terminally unsaturated carboxylic acid with either (1) asaturated aliphatic or saturated cycloaliphatic alcohol containing atleast two hydroxyl groups or, (2) a phenol containing at least twohydroxyl groups. Suitable alcohols and phenols can be represented by theformula HOR⁷ OH. Preferably R⁹ represents a single bond and R⁷represents unsubstituted alkylene containing from 2 to 10 carbon atoms,hydroxyl substituted alkylene containing from 3 to 10 carbon atoms orphenylene, this preference being based on the availability of thecorresponding alcohols and phenols.

Representative polyhydric alcohols include but are not limited toethylene glycol, the isomeric propylene glycols, glycerol,1,1,1-trimethylolpropane, 1,4-cyclohexanediol and other alcoholscontaining at least two hydroxyl groups per molecule and up to 20 ormore carbon atoms. Partially etherified polyhydric alcohols containingthree or more hydroxyl groups, at least two of which are unreacted, arealso suitable precursors for the alcohol portion of compoundscorresponding to embodiment B. Representative polyhydroxylated phenolsinclude the aforementioned hydroquinone and resorcinol.

It will be understood that the alcohol or phenol used to prepare theester must contain at least three unreacted hydroxyl groups if the finalcompound of this invention is to be represented by the foregoing generalformula 2 or 4.

The aforementioned class of terminally unsaturated carboxylic acidscontains from 3 up to 20 or more carbon atoms. Representative members ofthis class include acrylic acid, 3-butenoic acid, 9-decenoic acid and4-allylbenzoic acid.

A third embodiment of the present compounds, referred to hereinafter asC, is one wherein R¹ of the foregoing general formula is CH₂ ═CHR⁶ OR⁷,and R⁴ is CH₂ ═CHR⁶ OR¹⁰ <. The radicals represented by R⁶, R⁷ and R¹⁰are defined in the preceding paragraphs. Preferably R⁶ is an alkylenecontaining from 1 to 10 carbon atoms and R⁷ is alkylene or hydroxylsubstituted alkylene. *

In embodiment C, R¹ and R⁴ represent the residues remaining followingremoval of one and two hydroxyl groups, respectively, from the saturatedpolyhydric alcohol or polyhydric phenol portion of an ether derived fromthat alcohol or phenol and a terminally unsaturated alcohol or phenolcontaining one or more hydroxyl groups. Preferably the unsaturatedalcohol or phenol is monohydric. The saturated polyhydric alcohol orphenol can be any of those discussed hereinabove in connection withembodiments A and B, and the terminally unsaturated alcohol or phenolcan likewise be any of those discussed hereinabove in addition to allylalcohol. In an alternative of embodiment C, two hydroxyl groups of atrihydric alcohol such as 1,1,1-trimethylol propane are reacted with aterminally unsaturated alcohol such as allyl alcohol to form theterminally unsaturated organic compound. In this alternative embodimentR¹ is represented by the foregoing general formula (CH₂ ═CHR⁶ O)₂ R¹⁰--.

In the fourth embodiment of the present compounds, referred tohereinafter as D, R¹ of the foregoing general formulae 1 and 3 isdefined as CH² ═CHR⁶ OC(O)R⁸ -- and R⁴ of formulae 2 and 4 is defined asCH₂ ═CHR⁶ OC(O)R⁸ R¹⁰ <. In embodiment D, R⁸ represents a hydrocarbyleneradical selected from the same group as previously defined for R⁶.Preferably R⁷ represents alkylene containing from 1 to 10 carbon atomsand R⁸ represents alkylene containing from 1 to 10 carbon atoms,phenylene, hydroxyl-substituted phenylene or methoxy substitutedphenylene.

The R¹ and R⁴ substituents of the embodiment D represent the residuesremaining following removal of one and two hydroxyl groups,respectively, from the saturated or aromatic hydroxycarboxylic acidportion of an ester derived from that hydroxycarboxylic acid and any ofthe terminally unsaturated alcohols discussed in connection with thepreceding embodiments of the present compounds. It will be understoodthat the hydroxycarboxylic acid must contain two or more hydroxyl groupsper molecule to prepare a compound of this invention corresponding togeneral formula 2 or 4.

Hydroxcarboxylic acids useful for preparing compounds of embodiment Dinclude but are not limited to hydroxyacetic acid, lactic acid and theisomeric hydroxybenzoic, dihydroxybenzoic and dihydroxycinnamic acids.

Organosilicon compounds corresponding to any of the four embodiments(A-D) of this invention can be prepared by reacting an alkoxysilane ofthe general formula

    (R.sup.2 O).sub.4-p R.sup.3.sub.p Si                       Formula 14

or an alpha,omega-bis-trialkoxysilylhydrocarbon of the general formula

    (R.sup.2 O).sub.3 SiR.sup.5 Si(R.sup.2 O).sub.3            Formula 15

with one of the terminally unsaturated, hydroxylated organic compoundsdescribed in the preceding paragraphs. These organic compounds includeterminally unsaturated alcohols, ethers derived from a terminallyunsaturated alcohol and a saturated polyhydric alcohol, esters derivedfrom a terminally unsaturated carboxylic acid and a saturated polyhydricalcohol, and esters derived from a terminally unsaturated alcohol and ahydroxycarboxylic acid.

The reaction between the organic and organosilicon compounds describedhereinbefore in connection with the various embodiments of the presentcompounds is conducted under conditions that are typical forcondensation reactions involving alkoxysilanes and hydroxlated organiccompounds. These reactions are usually conducted under an anhydrousatmosphere such as nitrogen at temperatures from ambient to 200° C. andmay employ a catalyst. Useful catalysts include organic amines, tincompounds and titanium compounds. Specific catalysts include but are notlimited to stannous octoate, dibutyltin dilaurate and titanium compoundssuch as tetrabutyl titanate, Ti(OC₄ H₉)₄.

To function effectively the quantity of catalyst present must be solublein the reaction mixture. The weight of catalyst typically constitutesfrom about 0.1 to about 5 percent of the combined weight of allreactants.

Reactions involving replacement of silicon-bonded alkoxy groups generatethe alcohol corresponding to the alkoxide group as a by-product underneutral or acidic conditions. Because these reactions are oftenreversible, it is usually desirable to remove this by-product alcohol bydistillation as the reaction progresses. The course of the reaction canthen be readily followed by measuring the amount of alcohol collected.Because methanol and ethanol are the lowest boiling alcohols, it ispreferable that the alkoxy groups of the present organosiliconreactants, represented by OR² in the foregoing formulae 1-4 be methoxyor ethoxy.

The reactants and catalyst are preferably heated at a temperature offrom about 50° to 200° C. for a period of time sufficient to achieve asubstantially complete reaction, as indicated by the amount ofby-product alcohol collected. This time period is typically from 1 toabout 5 hours.

Some of the ethylenically unsaturated organic reactants used to preparethe compounds of this invention will polymerize at the temperatures usedto react them with the organosilicon compound. It may therefore bedesirable to include in the reaction mixture an effective amount of afree radical scavenger such as hydroquinone to completely suppress or atleast inhibit polymerization of the organic compound during preparationof the present compounds.

Those products of this invention having boiling points below about 200°C. under ambient or reduced pressure can be isolated by distilling theproduct from the reaction mixture. Higher boiling products can beisolated using known chromatographic techniques with gases or liquids asthe carrier.

For some end use applications of the present compounds, such as primersand adhesion promoters, the reaction mixture in which the compound isprepared can be used directly without isolation or purification of thecompound.

In some instances it may be desirable to include in the reaction mixturea liquid diluent that may also function as a solvent for the reactants.Suitable diluents include aliphatic and aromatic hydrocarbons that areliquid at ambient temperature and boil within the range of from 50° toabout 250° C. Representative diluents include hexane, heptane and liquidaromatic hydrocarbons such as benzene, toluene and xylene.

An alternate method for preparing the compounds of this inventioninvolves reacting one of the terminally unsaturated organic compoundsdescribed hereinbefore with an organosilicon compound corresponding tothe foregoing general formula 13 or 14, with the exception that one ofthe alkoxy groups is replaced with a chlorine atom. The reaction istypically conducted in the presence of a suitable acid acceptor. Theacceptor can be an organic amine such as pyridine.

The compounds of this invention contain two different classes ofreactive groups, namely a terminal carbon-to-carbon double bond and atleast two silicon-bonded alkoxy groups. Compounds of this type aresuitable for a variety of known end uses, including moisture activatedcrosslinking and chain extending agents for hydroxyl containingpolyorganosiloxanes.

The present compounds will react in the presence of moisture and asuitable catalyst to yield elastomeric or resinous materials, dependingupon the nature of the particular compound and other reactive materialspresent in the composition.

Compounds of this invention wherein R² and R³ of the foregoing formulae1-4 are methyl, R⁵ is ethylene, n is 1 or 2, p is 0 or 1 and r is 0constitute a preferred class of compounds that are particularly usefulas either primers or adhesion promoters for achieving cohesive bondingof polyorganosiloxane resins and elastomers to many inorganicsubstrates, including glass, steel and aluminum, and to some organicpolymers, particularly the class often referred to as engineeringthermoplastics. This class includes polyamides such aspoly(hexamethylene adipamide), polyesters such as poly(ethyleneterephthalate), polyimides and polysulfones.

Polyorganosiloxane compositions that are curable by a variety of meansto yield elastomers and resins are well known. Room temperature curablecompositions can be of two main types, namely one part compositionscurable in the presence of atmospheric moisture and two partcompositions curable by a hydrosilation reaction in the presence of aplatinum group metal or a compound thereof.

One part room temperature curable polyorganosiloxane compositionstypically contain a hydroxyl terminated polydiorganosiloxane with anaverage of 50 or more repeating units per molecule and a crosslinkingagent that is typically a silane containing at least threesilicon-bonded alkoxy or other hydrolyzable groups per molecule. Acatalyst such as a compound of tin or titanium is usually present toaccelerate the curing reaction.

Two part polyorganosiloxane compositions that are curable at roomtemperature can contain a liquid or solid polydiorganosiloxane having atleast two ethylenically unsaturated radical such as vinyl per moleculein combination with a crosslinking agent that is typically anorganosilicon compound containing at least three silicon-bonded hydrogenatoms per molecule. A small amount of platinum or a platinum compound isusually also present in these compositions as a hydrosilation catalyst.

Polyorganosiloxane compositions that cure at elevated temperatures cancontain a polydiorganosiloxane in liquid or solid form in addition to anorganic peroxide.

The aforementioned two part platinum catalyzed polyorganosiloxanecompositions that ordinarily cure at room temperature can be modified tocure only when heated by including in the composition one of the knownplatinum catalyst inhibitors. One such class of inhibitors are theacetylenic alcohols such as 2-methyl-3-butyn-2-ol.

The curable polyorganosiloxane compositions suitable for use incombination with the compounds of this invention as primers or adhesionpromoters can contain any of the ingredients conventionally present inthese compositions, including fillers, pigments and flame retardants.

Curable polyorganosiloxane compositions are sufficiently described inthe literature that a detailed discussion of these compositions in thisspecification is not required.

The present adhesion promoters are typically added to a curablepolyorganosiloxane composition in amounts of from 0.1 to about 10percent by weight, based on the weight of the total composition. Theadhesion promoters are particularly effective in combination withpolyoganosiloxane compositions that are cured by a hydrosilationreaction at room temperature.

When used as primers at least one member from the aforementioned classof preferred compounds of this invention is applied as a thin film to atleast one of the surfaces to be bonded. The compounds can be diluted ina suitable solvent to facilitate their application to a substrate.Solvents for the present preferred class of compounds include liquidhydrocarbons such as heptane, benzene, toluene and xylene, and themethyl and ethyl ethers of either ethylene glycol or propylene glycol.

Cohesive bonding of polyorganosiloxane elastomers or resins to amorphousor "glassy" organic polymers such as polymerized esters of acrylic ormethacrylic acids, polycarbonates and polystyrene can be achieved byusing the aforementioned preferred class of the present compounds asprimers in combination with copolymers derived from 1) at least oneethylenically unsaturated organic monomer such as styrene and esters ofmethacrylic or acrylic acid, and 2) a silane of the general formula

    RSiX.sub.3                                                 Formula 17

where R represents vinyl, allyl, or CH₂ ═CR'C(O)OR", R' is methyl orhydrogen, R" is alkyl containing from 1 to 4 carbons, and X represents ahydrolyzable group such as halogen, or lower alkoxy such as methoxy.These copolymers are disclosed in U.S. Pat. No. 3,306,800 that issued toE. Plueddemann on Feb. 26, 1967 and is incorporated herein by referenceas a teaching of primers that are suitable for use in combination withthe present adhesion promoters.

A particularly preferred class of copolymers is derived from methylmethacrylate and 3-methacroloxypropyltrimethoxysilane. The methylmethacrylate constitutes from 5 to about 95 weight percent of themonomer mixture, preferably from 80 to 95 weight percent.

The primer composition also contains a crosslinking agent for thecopolymers. Suitable crosslinking agents include organohydrogensiloxanescontaining an average of at least three silicon-bonded hydrogen atomsper molecule.

A mixture containing one or more of the copolymers described in theimmediately preceding paragraphs, one or more of the preferred compoundsof this invention and a crosslinking agent is applied as a primer to atleast one of the surfaces to be bonded. Alternatively, one of thepreferred compounds of this invention is blended together with a curablepolyorganosiloxane composition, and the copolymer and crosslinking agentare applied as a thin film to at least one of the surfaces to be bonded.

The following examples describe preferred embodiments of the presentcompounds and demonstrate their utility as adhesion promoters andprimers for polyorganosiloxane compositions. The examples should not beinterpreted as limiting the scope of this invention as defined in theaccompanying claims. All parts and percentages disclosed in the examplesare by weight unless otherwise indicated.

The general method used to prepare the exemplified compounds was to heata mixture containing a terminally unsaturated organic reactant, anorganosilicon compound and 1 percent of tetrabutyl titanate, based onthe total weight of the reaction mixture, in a reactor equipped tocondense and isolate liquid that vaporized from the reaction mixture.Heating of the reaction mixture was continued until the temperature ofthe reaction mixture reached between 100° and 110° C. for the silanereactants or from 110° to 166° C. for 1,2-bis(trimethoxysilyl)ethane.The amount of by-product alcohol, either methanol or ethanol, recoveredduring this heating period was substantially equal to the calculatedvalue based on the amounts of organosilicon and organic compoundspresent.

The organosilicon compounds used were tetramethoxysilane,tetraethoxysilane, methyltrimethoxysilane, phenyltrimethoxysilane, and1,2-bis(trimethoxysilyl)ethane. Reaction mixtures containing the foursilanes were heated until the temperature of the reaction mixturereached a value within the range from 100° to 110° C. to preventexcessive distillation of silane from the reaction mixture. Reactionmixtures containing bis(trimethoxysilyl)ethane could be heated to 160°C. Without substantial loss of this reactant by distillation.

EXAMPLE 1

Compounds of this invention were prepared by combining a terminallyunsaturated organic compound, an organosilicon compound containing atleast three silicon-bonded methoxy or ethoxy groups per molecule and 1%,based on the total weight of the reaction mixture, of tetrabutyltitanate. The resultant mixture was heated with stirring while removingvolatile materials by distillation. Heating was continued until anamount of alcohol equivalent to a substantially complete reaction wasisolated from the reaction mixture.

The types and molar ratios of reactants and the final temperature of thereaction mixture are listed in Table 1. The reactants used arerepresented by the following abbreviations. Unless otherwise indicated,the final temperature of the reaction mixture was within the range from100° to 110° C.

ORGANIC REACTANTS

U: 10-undecenol

E: Eugenol

HEA: Hydroxyethyl acrylate

HPA: Hydroxypropyl acrylate

MATMP: Monoallyl ether of 1,1,1-trimethylolpropane

DATMP: Diallyl ether of 1,1,1-trimethylolpropane

PB: A hydroxyl endblocked polybutadiene corresponding to the averageformula ##STR2## This polymer is available as Poly BD R-45M from ArcoChemicals. AE: 2-Allyloxy-1-ethanol

AP: o-Allylphenol.

ORGANOSILICON REACTANTS

TMS: Tetramethoxysilane

MTMS: Methyltrimethoxysilane

PTMS: Phenyltrimethoxysilane

TES: Tetraethoxysilane

TMSE: 1,2-bis(trimethoxysilyl)ethane.

                  TABLE 1                                                         ______________________________________                                        Product              Molar Ratio Final Reaction                               No.     Reactants    of Reactants                                                                              Temperature                                  ______________________________________                                         1      U/TMS        1/1                                                       2      E/TMS        1/1                                                       3      HPA/TMS*     1/1                                                       4      MATMP/TMS    1/1                                                       5      MATMP/MTMS     1/1.1     120° C.                                6      MATMP/MTMS     1/2.2     110° C.                                7      MATMP/TES    1/1                                                       8      MATMP/PTMS   1/1                                                       9      PB/MTMS      1/1                                                      10      AE/MTMS      1/1                                                      11      E/MTMS       1/1                                                      12      AP/MTMS      1/1                                                      13      MATMP/TMSE   1/2         150° C.                               14      DATMP/TMSE   1/1         160° C.                               15      HEA/MTMS*    1/1                                                      ______________________________________                                         *0.004% of hydroquinone was added to the reaction mixture as a                polymerization inhibitor                                                      **100-110° C. unless otherwise specified                          

EXAMPLE 2

This example demonstrates the efficiency of representative compounds ofthis invention as adhesion promoters for cohesively bonding apolyorganosiloxane elastomer to glass and metal substrates. A curable,pumpable polyorganosiloxane composition was prepared by blending thefollowing ingredients to homogeniety:

101.3 parts of a dimethylvinylsiloxy endblocked polydimethylsiloxanehaving a viscosity of about 3 Pa.s at 25° C.;

34.7 parts of a benzene soluble resinous copolymer containingtriorganosiloxy units and SiO₂ units in the mol ratio of about 0.7 molof triorganosiloxy unit per mol of SiO₂ unit where the triorganosiloxyunits are trimethylsiloxy units and dimethylvinylsiloxy units and thecopolymer contains from 1.4 to 2.2 weight percent of silicon-bondedvinyl radicals;

48.9 parts of fume silica;

0.7 part of water;

0.31 part of a hydroxyl terminated polydiorganosiloxane containingdimethylsiloxane and methylvinylsiloxane units about 10 weight percentvinyl radicals and about 16 weight percent hydroxyl radicals;

8.14 part of hexamethyldisilazane;

5.28 parts of a trimethylsiloxy endblocked polydiorganosiloxane havingan average of five methylhydrogensiloxane units and threedimethylsiloxane units per molecule with a silicon-bonded hydrogen atomcontent in the range of 0.7 to 0.8 weight percent;

0.15 part of a curing catalyst in the form of a chloroplatinic acidcomplex of divinyltetramethyldisiloxane that had been diluted with aliquid dimethylvinylsiloxy terminated polydimethylsiloxane to achieve0.7 weight percent platinum; and

0.015 part of 2-methyl-3-butyne-2-ol as a catalyst inhibitor.

Samples of this composition were blended with 1 percent by weight ofcompounds 1-5 and 7-12 listed in the foregoing Table 1. A 3.2 mm-thicklayer of the resultant composition was applied as a 2.5 centimeter-widestrip to a glass microscope slide, to sheets of cold-rolled steel andaluminum, and to brass shim stock. The coated substrate was cured forfrom 5 to 7 minutes at a temperature of 150° C.

The adhesion of the elastomer to the substrate was evaluated byloosening one of the 2.5 cm.-wide edges of the cured coating with arazor blade. A weight of about 0.1 kilogram was attached to thisloosened edge strip and allowed to hang free in an attempt to peel theremainder of the coating from the substrate. The coated surface wasmaintained in a substantially horizontal plane and the amount of weightwas gradually increased to 10 kilograms, If the coating separated fromthe substrate, the weight (i.e. the force) being applied at the time offailure was recorded, and the failure was rated an adhesive one.Coatings which could not be peeled from the substrate under a force of10 kg. were rated as being cohesively bonded to the substrate.

A substrate coated with a cured elastomer prepared as described in thepreceding paragraph but which did not contain an adhesion promoter wasused as a control. The amount of force, i.e. the amount of weightattached to the coating, being applied at the time separation of thecoating from the substrate occurred was 0.9 kg. for glass, 0.1 kg. forcold rolled steel, 0.2 kg. for aluminum and 0.5 kg. for brass.

All of the elastomers with the exception of the one prepared usingcompound 7 from the preceding Table 1 exhibited cohesive bonding to allsubstrates. The elastomer prepared using compound 7 was cohesivelybonded to glass and brass, but separated from cold rolled steel andaluminum under applied weights of 2.5 and 1.6 kg., respectively, whichrepresented a significant improvement over the control. In all instancesthe weight required to achieve peeling of the control coating from thesubstrate was less than one kilogram.

EXAMPLE 3

This example demonstrates the performance of a primer compositioncontaining one of the preferred compounds of this invention incombination with a known primer for adhering inorganic reinforcingagents to organic polymers.

The primer was prepared by homogeneously blending 2 parts of compound 15from Table 1 of the preceding Example 1, 10 parts of a 20 percentsolution in ethyl acetate of a methylmethacrylate/3-methacryloxypropyltrimethoxysilane copolymer, 87 parts ofthe monomethyl ether of propylene glycol, and 1 part of atrimethylsiloxy endblocked polymethylhydrogensiloxane having a viscosityof about 0.13 Pa.s at 25° C. and a silicon-bonded hydrogen atom contentof about 1.6 percent by weight.

The copolymer was prepared by reacting methyl methacrylate and3-methacryloxypropyltrimethoxysilane in a molar ratio of 10:1,respectively, in the presence of 1 percent by weight, based on totalmonomers, of 3-mercaptopropyltrimethoxysilane and a catalytic amount ofbenzoyl peroxide. The polymerization was conducted in ethyl acetate.

The ability of the primer to cohesively bond a polydimethylsiloxaneelastomer to both polymethyl methacrylate and a polycarbonate wasevaluated using a modification of ASTM test procedure No. D 1002.

Samples of polymethyl methacrylate (A) and a polycarbonate (B) in sheetform were cleaned by wiping them with hexane followed by a wiping withmethanol. The samples measured 2.5 cm in width and 7.6 cm in length.After the samples had dried, a film of the primer composition wasapplied by wiping with a clean cloth. The samples were then allowed toair dry for 20 minutes before a second coating of primer was wiped on inthe same manner as the first coat. After drying in air for 90 minutes, a2.7 cm.-wide strip of curable polymethylsiloxane elastomer was appliedto one end of the primed surface either sample A or B. One end of theprimed surface of the other sample was placed in contact with oppositesurfaces of the elastomer layer to achieve an overlap of 2.5 cm. betweenthe polycarbonate and polymethylmethacrylate samples. The elastomer wascurable by a platinum catalyzed hydrosilation reaction and exhibited adurometer of 50 on the Shore A scale following curing.

The laminate of polycarbonate and polymethyl methacrylate samplesseparated by the layer of cured elastomer was placed in a jig thatmaintained the thickness of the elastomer layer at 1.3 mm during curing.The resultant assembly was then placed between the platens of a pressthat was heated to a temperature of 100° C. The platens of the presswere adjusted to maintain a pressure of 345 KPa on the sample for twohours. The assembly was then removed from the press and allowed toequilibrate under ambient conditions for at least 16 hours prior tobeing tested.

Testing of the samples to determine the strength and nature of the bondbetween the elastomer and the two organic polymers was conducted underthe conditions specified in ASTM test procedure No. D 1002. The load atfailure and the type of failure were noted. The three samples testedfailed at loads of 2622, 2746 and 2863 kPa. In all instances the failurewas cohesive, i.e., the elastomer tore while retaining adhesion to bothsubstrates over the entire contact area.

That which is claimed:
 1. A primer composition for adhering a curablepolyorganosiloxane elastomer composition to an inorganic substrate, saidprimer composition comprising an organosilicon compound having a generalformual selected from the group consisting of

    (R.sup.1 O).sub.n (R.sup.2 O).sub.4-n-p R.sup.3.sub.p Si,

    R.sup.4 [OSi(OR.sup.2).sub.3-p R.sup.3.sub.p ].sub.2,

    (R.sup.1 O).sub.n (R.sup.2 O).sub.3-n SiR.sup.5 Si(OR.sup.1).sub.2 (OR.sup.2).sub.3-r,

and

    R.sup.4 [OSi(OR.sup.2).sub.2 R.sup.5 Si(OR.sup.2).sub.3 ].sub.2,

where R¹ represents a radical selected from the group consisting of

    CH.sub.2 ═CHCH.sub.2 R.sup.6 --,

    CH.sub.2 ═CHR.sup.6 OR.sup.7 --,

    CH.sub.2 ═CHR.sup.6 OC(O)R.sup.8 --,

    CH.sub.2 ═CHR.sup.9 C(O)OR.sup.7 --,

and

    (CH.sub.2 ═CHR.sup.6 O).sub.2 R.sup.10 --;

R² and R³ are methyl; R⁴ represents a radical selected from the groupconsisting of

    CH.sub.2 ═CHR.sup.10 <,

    CH.sub.2 ═CHR.sup.6 OR.sup.10 <,

    CH.sub.2 ═CHR.sup.6 OC(O)R.sup.10 ═

and

    CH.sub.2 ═CHR.sup.9 C(O)OR.sup.10 ═;

R⁵ represents ethylene; R⁶ represents a hydrocarbylene or substitutedhydrocarbylene radical where the substituent is hydroxyl or alkoxy; R⁷is selected from the same group as R⁶ or represents anallyloxy-substituted hydrocarbylene radial, with the proviso that R⁷contains at least 2 carbon atoms; R⁸ is selected from the same group asR⁶ ; R⁹ represents a single bond or a radical selected from the samegroup as R⁶ ; R¹⁰ represents a trivalent hydrocarbon radical; n is 1 or2; p is 0 or 1; r is 0 or 1; and 4-n-p is at least
 2. 2. A primercomposition according to claim 1 where R⁶ is alkylene, phenylene, alkoxysubstituted phenylene or the residue remaining following removal of oneterminal hydroxyl group from a hydroxyl terminated polybutadiene havingan average degree of polymerization of between 50 and
 60. 3. A compoundaccording to claim 1 where R¹ is CH₂ ═CHR⁶ OR⁷ --, R⁶ is methylene andR⁷ is ##STR3##
 4. A primer composition according to claim 1 where R¹ isCH₂ CHR⁶ OC(O)R⁸, where R⁶ represents alkylene containing from 1 to 10carbon atoms, and R⁸ represents alkylene containing from 1 to 10 carbonatoms, phenylene, hydroxyl substituted phenylene or methoxy substitutedphenylene.
 5. A primer composition according to claim 1 where R¹ is CH₂═CHR⁹ C(O)OR⁷ --, and where R⁹ represents a single bond and R⁷represents alkylene containing from 2 to 10 carbon atoms, hydroxylsubstituted alkylene containing from 3 to 10 carbon atoms or phenylene.6. A primer composition according to claim 1 where R¹ is (CH₂ ═CHR⁶ O)₂R¹⁰, R⁶ is methylene and R¹⁰ is ##STR4##
 7. A primer compositionaccording to claim 1 where R⁴ is CH₂ ═CHR¹⁰, where R⁶ is methylene andR¹⁰ is ##STR5##
 8. A primer composition according to claim 1 where saidprimer includes a copolymer consisting essentially of from 10 to 95weight percent of repeating units derived from3-(methacryloxypropyl)trimethoxysilane and from 5 to 90 percent byweight of repeating units derived from methyl methacrylate.
 9. A primercomposition according to claim 8 where said silane constitutes from 40to 60 weight percent of the combination of said compound and saidcopolymer.
 10. A primer composition according to claim 9 where saidorganosilicon compound exhibits the general formula CH₂ ═CHR⁶ OR⁷ -- or(CH₂ ═CHR⁶ O)₂ R¹⁰ where R⁶ is methylene, R⁷ is ##STR6## and R¹⁰ is##STR7##